We circumnavigated AZ and ended up at Zion and Bryce Canyon.
Crossing southern AZ or any other desert, you by gas at any opportunity, once you drop below 1/2 tank.
Also as mentioned, 5 gallons of stabilized gas provides a lot of peace of mind.
I have stopped at some tiny gas stations and had to move a "Mulch for sale" sign once to exit. I also banged up my skid plate on a very steep exit.
Given my choice, I will favor the large truck stops or a station with an easy in-easy out pump set up.
I have never notice any significant price differences between stations in a given area and I certainly am not going to drive five miles out of my way to save a dollar on a 20 gallon fill up.